Lubricating oil refining



Mayll, 1937. P..KE|TH,JR.. ETAL 2,079,911

LUBRICATING OIL REFINING Filed June 28, 1954 Henry O. Fogrt ATTORNEYPropane Deczsp/zltn Propane Patented May 11, 1937 LUBRICATIN G OILREFINING Percy C. Keith, 'Jr., Peapack, and Henry 0. Forrest, Teaneck,N. J., assignors to Standard Oil Company, Chicago, lll.; a corporationof Indiana Application Junees, 1934, serial No. '132,918

9 Claims.

The object of our invention is to obtain maximum eiectiveness ofnaphthenic solvent and to obtain maximum yields of premium and highgrade oils from any given stock with minimum installation and operatingcosts. A further object is to provide an improved process wherein theasphaltic and/or naphthenic products produced in the system maysupplement the action of the naphthenic solvent' without contaminatingthe high quality paraiiinic oil. provide a system for recovering anintermediate grade of paraflinic oilv from asphaltic and/or naphthenicoil fractions. A further object-is to increase the e'iciency andeffectiveness of a batch countercurrent propanenaphthenic solventsystem. Other objects will be apparent as the detailed description ofour invention proceeds.

In practicing'our invention we rst effect a separation of asphalticcomponents from parafof naphthenic solvents. This step is preferablyeiected by precipitation from a propane solution either at high or lowtemperatures. 'I'he propane solution is then extracted with a naphthenicsolwe have Idiscovered that by adding asphalttoA the solvent extractionextract before-washing it with propane we can increase the-yield andquality of second grade oil obtainable from any given stock and thatsimilar results can be obtained by recycling a portion of the nalextract through the countercurrent propane system. We

believe that the oil or extract itself acts in the A further Objectistoy nic and naphthenic components in the absence (Cl. ISG-13) nature ofa selective solvent and that the presence oi this asphaltic precipitateorthis recycled extract causes further phase separation in thecountercurrent propane washing system. However, we do not limitourselves to any particular theory since it is the process itself andthe new, unexpected and important results accomplished thereby whichcharacterize our invention.

The invention will be more clearly understood from the accompanyingdrawing which forms a part of this specification and which illustrates adiagrammatic plan of our improved system.

`In the following description we will disclose the rening of an S. A. E.Mid-Continent steam refined stock. It should' be understood, however,that the invention is equally applicable to distillate as well asresidual stocks o f grades from S. A. E. 10 to S. A. E. 70 whether ornot they have been subjected to acid treatments or other refineryoperations. We will describe the use of cresylic acid as our selectivenaphthenic solvent, but it should be understood that this is only 'anexample of a naphthenlc solvent and we contemplate the use of anyequivalent solvent or solvent mixture, particularlyl a solvent such asphenol, cresol, ortho, meta and para cresylic acids, nitrobenzen'e, furfural, dichlorethyl ether, -chloraniline, chlorphenol, sulfur dioxide,benzol, etc. and mixtures of two or more of said solvents. We willdescribe`\propane as the deasphalting and washing agent, but it shouldbe understood that we contemplate the use of other normally gaseoushydrocarbons such as -ethane, butane, isobutane, `cyclopropane,propylene, ethylene, etc. and mixtures of the same. The presentinvention relates primarily to process steps and it should be understoodthat suitable solvents may be used which will serve the same purpose asthe solvents herein described.

The S. A. E. 40 steam rened Mid-Continent y lubricating oil stock isintroduced directly from a pipe still or from a suitable storage tankthrough line Ill to deasphalting vessel Il. This vessel shouldpreferably be designed to withstand pressures of from 600 to 1000 poundsper square inch and it should beprovlded with sultable drawoff means forseparating the liquid layers which are formed in the deasphalting step.Propane may be introduced through line I2 into line l0, preferablythrough suitable mixing ap' paratus and the mixture may be passedthrough a suitable heat exchanger I3 before being introduced into thedeasphalting vessel. Heating and cooling coils may, of course, beemployed in the deasphalting vessel itself.

- vailing in the solvent extraction system.

The temperature of the deasphalting stage will depend upon the nature ofthe oil stock and the nature of the desired products. If wax is presentwe prefer to deasphalt at temperatures above 100 F., so that the waxwill be carried in the propane solution with the oil. As the temperatureis increased from 100 F. to the critical temperature of propane, moreand more asphaltic material is thrown out of the solution, together withcolor bodies and resinous materials. It seems that this fractionation ison the basis of molecular weight, the extremely high molecular weightsubstances being thrown out of the solution.

We may eiect the deasphalting at low temperatures and, in fact, we mayprecipitate the asphaltic material with the wax and remove the twosubstances together. Vantageous for distillate stocks and stockscontaining only small amounts of asphalt and we have found that theasphalt itself assists in dragging the solidied wax out of the solution.The

asphalt is discharged through pipe I@ to storage tank I5 and the propanesolution is discharged through pipe I6 or pipe I6 to propane dewaxingchiller l1 or I1'. The propane solution may be chilled to 40 F. byvaporizing propane therefrom and this cold slurry may be passed fromchiller -l1 through pipe I8 or i8 to filter I0 or to any other Wellknown means for separating wax from diluted oil.

The dewaxed filtrate (wax yfree diluted oil') may be introduced throughpipe 20 to solvent extraction system 2i or the propane solution directlyfrom the deasphalting system may be bypassed through line 22 to thesolvent extraction system. It should be understood that the amount ofpropane in the oil as it enters the solvent extraction system may bevaried in order to obtain a maximum miscibility temperature'with thesolvent or, in other Words, to obtain maximum phase separation. A

The solvent extraction system may be a continuous horizontal extractorwherein solvent is flowed continuously in one directionand the oil isowed in the opposite direction with mixing and settling means interposedalong the length of the extractor to provide intimate contact and toprevent short circuiting during the extraction step. 'I'he finalramnate, together with propane and some solvent, is withdrawn throughline 23 and reduced in a suitable steam or vacuum still to free thepara'inic oil from propane and solvent, both -of which are recovered forreuse. This rainate is the premium or rst grade high quality lubricatingoil.

The solvent is introduced into the system through line 24 and it isremoved with extract through line 25. This extract contains naphthenicoil components, but it also contains paraiiinic components which aremiscible with the naphthenic components under the conditions pre- In0rder to recover additional parafnic components from the extractor, weemploy a batch countercurrent propane washing system, the extract beingintroduced into the first stage 26 thereof and through pipe 3|.

the propane being introduced into the last stage 21 thereof through line28. Ranate from stage 21 is introduced through pipe 23 to stage 30 inadmixture with extract withdrawn from stage 26 Rainate from stage 30 isintroduced through pipe 32 to stage 26, together with extract from line25 and with asphaltic or naphthenic material as will be hereinafter de-This process is ad,

ao'zaarr We have discovered that both the amount and quality of thissecond raflinate may be markedly increased by the introduction ofnaphthenic or asphaltic components with the extract into stage 26.Asphalt may be introduced from storage tank l5 by means of line 36 ornaphthenic material may be recycled through line 31. 'I'hus We mayoperate our process either with asphalt from line 36, naphthenicmaterial from line 31, or both, and by this reintroduction or recyclingof asphaltic or naphthenic material we nd that the quality and yield ofthe Second grade paratnic lubricating oil is substantially increased.

Although we have shown the propane dewaxing system placed between thedeasphalting and the solvent extraction steps, it should be understoodthat `the dewaxing may be efected after the solvent extraction step orwith the deasphalting step. A particularly simple method of procedure isto precipitate both asphalt and wax from the propane solution in vesselIl at temperatures of 40 F. or lower, to remove the cold 'propanesolution for solvent extraction through lines I6 and 22, and then toheat the remaining mixture in vessel H with additional propane to hightemperatures at which the wax is in solution and the asphalt is thrownout of solution. This makes possible a liquid phase dewaxing which ismuch simpler and much less expensive than the ordinary dewaxing. Theasphalt may be withdrawn through line itl to storage and the hot waxsolution through line 38 to a propane still and then to storage. Itshould be understood that if this batch method is used for deasphaltingand dewaxing it may be necessary to employ a collector or feed tank sothat the extraction process may be continuous. The drawing isdiagrammatic and does not purport to show the necessary pumps, storagetanks', piping, valves, stills, etc., the proper use of which is wellknown to those skilled in the art.

While we have described in detail a preferred embodiment of ourinvention, it should be understood that we do not limit ourselves tosaid details except as dened by the following claims, which should beconstruedas broadly as the prior art will permit.

We claim: v

1. The method of reining a lubricating oll containing naphthenic,paralnic and asphaltic components which comprises treating said oil withliquid propane under pressure to separate asphaltic components from a.propane solution of parainic and naphthenic components, countercurrentlyextracting said solution with a naphthenic solvent to separate parainiccomponents from naphthenic components, and separately washing theextract from the countercurrent extraction step with propane in thepresence of asphaltic material precipitated in the first step of theprocess whereby a second grade paraflinic lubricating oil is produced.

2. The method of refining a lubricating oil containing paraiinic,naphthenic and asphaltic components which comprises separating asphalticcomponents from a propane solution of naphthenic .and parainiccomponents, countercurrently extracting said solution with a naphthenicsolvent, washing parafnic oil out of the extract from saidcountercurrent extraction process in a countercurrent batch propanesystem to form a second grade paraffinic oil and a iinal extract, and

recycling a portion of the final extract to the first stage of thecounterourrent batch propane washing system whereby the yield andquality of the second grade raiiinate is improved.

3. 'I'he method of claim 1 wherein wax is separated from the paranic oilwhile it is in propane solution.

4. The combination of claim 2 wherein wax is removed from the parailinicoil while it is in propane solution.

5. The method of increasing the yield and quality of a second gradeparaiiinic oil obtained by Washing a solvent extraction extract (fromwhich the selective naphthenic solvent has not been reymoved) withpropane which comprises adding an asphaltic material to the extractundergoing washing.

6. The method of increasing the yield of parafnic mineral lubricatingoils from a lubricating oil stock consisting chiefly of naphthenic andasphaltic components, which method comprises countercurrently washingsaid stock with propanein the presence of a naphthenic solvent,

whereby the propane dissolves the paraiiinic'oil 40 components,extracting said mixture of paraflnic and naphthenic components with aselective solvent for removing naphthenic components -from paralnlccomponents, removing said solvent which contains naphthenic componentstogether with a small amount of parafiinic components from the separatedparaiiinic components, adding asphalt to said solvent mixture to cause afurther separation of paraiiinic components from naphthenic components,removing said separated paraftlnic components from thesolvent-asphaltnaphthenic component mixture and recovering solvent fromeach of said paraflinic components and vfrom the asphalt-naphtheniccomponent mixture.

8. The method of rening a mineral oil containing parainic components,naphthenic components and asphalt which comprises treating said oil withliquid propane under conditions adapted to cause separation of asphalt,extracting the propane-soluble fraction with a selective solvent, andtreating the asphalt from the rst step simultaneously with additionalpropane and with extract material from the second step to recoverparafilnic components which would otherwise be discarded with asphaltand extract.

9. The method of recovering relatively paraflinic hydrocarbons containedin an asphaltv and in an 1 taining said relatively parafnic hydrocarbonsin solution from the remaining materials.

PERCY C. KEITH, JR. HENRY O. FORREST.

